1. Field of the Invention
The present invention relates to a vehicle such as an automobile or an off-road vehicle such as an off-road car and a golf cart, and also relates to a wheel suspension device for the vehicle and to a method of assembling the vehicle.
2. Description of the Related Art
A known wheel suspension device of an automobile or an off-road vehicle includes a four-wheel independent suspension system in which front and rear wheels are each held by an independent suspension device of a double wishbone type. This suspension system has lower and upper arms extending laterally from a total of four locations on both sides in the front and both sides in the rear of a body frame, and knuckles connected to the forward ends of both of these arms for supporting wheels for rotation.
Each of the upper and lower arms in each location has a body frame side end that is wider than a knuckle side end and the body frame side end is connected to the body frame at two spaced-apart locations for pivotal movement in the vertical direction. Each of the knuckle side ends of the upper and lower arms on both sides in the rear is connected to the knuckle at one location or two spaced-apart locations for pivotal movement in the vertical direction. On the other hand, the knuckle side ends of the upper and lower arms on both sides in front are connected by being fitted to ball joints provided on the knuckles, respectively, with the knuckles being rotatable relative to the upper and lower arms in both vertical and lateral directions. Also, at least one cushion unit is disposed at each of the two sides in the front and the at least one cushion unit is connected at one end to at least one of the upper and lower arms for pivotal movement about its longitudinal shaft. The cushion unit includes a compression coil spring and/or a shock absorber arranged parallel to the compression coil spring. The other end of the at least one cushion unit is connected to the body frame for pivotal movement about the longitudinal shaft.
In the knuckle on the side of at least one drive wheel of the front and rear wheels, a wheel support shaft penetrates the knuckle in the lateral direction and is supported for rotation. The wheel support shaft is connected at its body frame side end to a drive shaft and a wheel is fixed to the wheel support shaft at the end on the opposite side from the body frame side end with respect to the knuckle. The drive shaft is provided at both ends with universal joints and is telescopic in the axial direction. This allows a rotational drive force to be transmitted satisfactorily to a wheel from a drive source disposed on the body frame even if the wheel makes a swinging movement or is turned about the vertical shaft with respect to the body frame.
Also, a device of a four wheel independent suspension system shown in FIG. 3 and FIG. 4 of JP-B 3069309, for example, is of a four-wheel drive type, in which at each of a total of four locations on both sides at the front of the body frame and both sides in the rear of the body frame, the lower arm arrangement is replaced by a tension rod and a drive wheel having universal joints disposed at both ends, and the cushion unit is connected at one end to an upper arm and at the other end to the body frame for pivotal movement about the longitudinal shaft, respectively.
The vehicle equipped with such a wheel suspension device as described above is manufactured by the so-called flow operation. That is, vehicles of this type are manufactured in such a manner that body frames are supplied to a production line and parts are mounted to the body frames successively.
Since, in the vehicle equipped with a conventional wheel suspension device described above, parts such as the upper and lower arms and cushion units of the wheel suspension device, and wheel driving reduction gears, are mounted to the body frame on a production line, a lot of work-hours are required for the assembly work to be performed on the production line. In addition, auxiliary work must be performed on the production line, such as connecting knuckles to the upper and lower arms and connecting the reduction gears to axles provided in the knuckles.
Therefore, a long production line is needed and if some problem occurs such as a shortage of parts, it will impact the whole production line, resulting in a large decrease in production efficiency. Also, if the quantity of the production lot becomes smaller, the frequency of the set-up change is significantly increased, so that a large decrease in production efficiency occurs if the production line is long. Therefore, in some cases, assembling costs become much higher than expected.
Further, in the vehicle equipped with independent suspension type wheel suspension devices, when a wheel travels over irregularities on the road during travel, shocks are transmitted to the body frame through the upper and lower arms and cushion units. However, riding comfort is not necessarily improved, depending on the shock-absorbing property of the cushion unit. In addition, since shocks are applied to the body frame from the suspension device in each wheel as described above, portions of the body frame to which the wheel suspension devices are connected must be stronger and more rigid than other portions.
Further, in the vehicle equipped with the above-described conventional wheel suspension devices, unless all the constituent members of the wheel suspension device are formed with very high accuracy and all the wheel suspension device-connecting portions of the body frame are formed with very high accuracy, it is impossible for the wheel suspension device to be mounted to the body frame. Therefore, in some cases, the foregoing conventional vehicle increases costs in forming the foregoing constituent members and suspension device-connecting portions.